I have a Validation rule that i place on a flow action so that when i submit the Birthday (of type DATE) will be checked to be smaller than 18 years.

The validation rule can be found bellow:

@if(@(Pega-RULES:ExpressionEvaluators).round(@(Pega-RULES:DateTime).DateTimeDifference(.Birthday+"T000000.000 GMT",@(Pega-RULES:DateTime).CurrentDateTime(), "Y")) < 18,true,false)

The first time  I press Submit (and the Birthday property is not valid), the error message appears correctly, where it should, just under the Birthday picker.

If i leave everything unchanged and I press Submit( in our case the  Weiter" button which has Finish Assignment action) one more time, the error message disappears and appears in the top part of the section like in the image bellow.

If a third time i press submit without changing anything the error message will be displayed correctly like in the first case.

This behaviour is strange and I do not know if it is a Pega bug or some implementation bug. Also after the second submit pyWorkPage is not displayed with red( like it should because an error is present) and everything appears to be ok on the clipboard. Could anybody please explain this strange behaviour? In both cases the error message is the same.